This invention relates generally to forming tubular or channel parts in a T-joint. More specifically, this invention relates to a method of joining said parts by a riveting and brazing method. The invention is useful in joining, e.g., hydroformed parts, in vehicle body or frame assembly.
Automobiles, and other such motor vehicles, often include a frame and body assembly comprising several unique structures and/or shapes. In the past, vehicle body structures comprised panel and frame members, usually metallic such as steel. Steel has typically been used because of its relatively high strength, low cost and the ease by which it can be shaped into frame members or body panels. Recent studies have developed vehicular body structures that include relatively lighter materials, such as aluminum or magnesium, and/or irregularly shaped, thin-walled hydroformed structures that are designed to reduce the number of parts and the overall weight of the automobile.
The driving force for the introduction of hydroformed parts into the automotive industry is the desire to reduce the manufacturing cost and weight by consolidating parts. However, the application of tubular hydroformed parts for vehicle structures creates problems in vehicle fabrication and assembly. The joining of two hydroformed parts in a T-like joint has proven difficult. Attaching two tubular parts, or a channel-shaped part and a tubular part, at a right or an acute angle can be done by conventional welding techniques, such as spot welding or other fusion welding. However, it is sometimes difficult to fit the parts together. Moreover, the application of welding heat to relatively small areas of the thin-walled bulky structures often produces distortion of the parts at the weld region. This distortion can occur in the joining of steel parts but is particularly problematic in the joining of lower melting, lighter weight parts, such as those of aluminum or magnesium alloys.
Thus, it is an object of the present invention to provide a new method for joining tubular or tubular and channel-shaped components in a T-shaped joint. It is a further object to employ such a method that utilizes lower temperatures and less heat so as to minimize distortion of metal in the region of the T-joint. Such a method would have particular utility in joining thin-walled hydroformed parts or the like.
This invention provides a riveting/brazing process, which results in less heat distortion than is usually encountered in welding thin-walled tubular and/or channel parts in a T-joint. In making such a joint, the end of a first tubular or channel member must be attached at an acute or right angle to the side surface of a second tubular or channel member.
In accordance with the invention, one or more flanges are cut into one end of the first member. The purpose of the flange is to provide integral material of the first member to be attached to the surface of the second member. The flange is cut so that it can be shaped in conformance with the surface of the second member. Corresponding location holes are formed both in the flange(s) as well as in the intended joint surface of the second member. These location holes are made to achieve suitable alignment of the end of the first member with the joint surface of the second member. A brazing alloy is fixed to a side of the flange, or forming the flange to the surface of the second member. The flange(s) are attached to the surface of the second member by means of a rivet to form an assembly. Once completed, heat is applied to the assembly to form a brazed joint.
The flanges are formed on one end of the first member by cutting them into shapes that will allow good contact with the surface of the second member. For more complex structures, such as cylindrical tubes, several flanges may be necessary to accomplish a secure fit among the parts. Accordingly, a flange is to be cut and shaped so that it can be pressed into suitable conformance with the shape of the second member.
In a preferred embodiment of the invention, a pocket is formed in the surface of the flange(s) to receive a body of braze alloy filler material. The pocket can be shaped to accommodate the brazing alloy, which is suitably in the form of a rod, a ring, or a flat sheet. In a particularly preferred embodiment, the pocket is formed in the surface of the flange(s) so that the body of braze material protrudes about 0.01 to 0.5 millimeter. When the flange and protruding braze alloy is placed into contact with the forming surface, a space is provided for flow of molten braze alloy to bond the assembled flange and the surface of the second member.
In another preferred embodiment of the invention, each flange is attached to the surface of the second member, prior to brazing, by placing a rivet through their corresponding location holes. The rivet is sized to allow a suitable connection between the flange and the second member to accommodate the above-described brazing gap between the parts. Thus, the brazing alloy can better flow, from the pocket into the brazing gap, upon application of heat.
Other objects and advantages of this invention will become apparent from a detailed description of specific embodiments that follow.